The present invention is directed generally to a fluid supply assembly for a fluid applicator, and more particularly to a fluid supply assembly with a disposable cup and lid, and a reusable shell and outer lid.
Some fluid applicators, such as gravity feed paint spray guns, have a fluid supply cup mounted on top of the fluid applicator. The fluid supply cup is typically reusable. Fluid, such as paint, is generally measured and mixed in a separate container, and then poured into the fluid supply cup for use. The container for measuring and mixing must be either cleaned or disposed of. During fluid application, the user must be careful not to tip the fluid applicator too much, or fluid will leak out a vent in the fluid supply cup. In addition, the user cannot use all of the fluid because it moves around in the fluid supply cup and air can be drawn into the drain hole.
Attempts have been made to provide fluid supply assemblies which reduce the amount of cleaning required after use. For example, U.S. Pat. No. 5,582,350 describes a hand held spray gun with a top mounted paint cup which extends from the rear of the gun body at an angle of 30°±10°. The paint can be sealed in a collapsible closed bag in the paint cup. Using the closed bag, the gun can be operated at all angles without the paint leaking. The use of the closed bag also allows more of the paint to be used. In addition, it reduces cleanup time and cost because the bag keeps the paint cup clean. Thus, U.S. Pat. No. 5,582,350 represented a significant advance in the art.
The use of the combination of an exterior container and a collapsible cup-shaped liner as a fluid supply assembly is also known. For example, U.S. Pat. No. 6,820,824 describes a spray gun with a fluid reservoir containing a removable liner. The liner, which may be thermo/vacuum-formed from a plastics material, has a shape corresponding to, and is a close fit within, the interior of the reservoir and collapses as fluid is withdrawn from within the liner during operation of the gun. Preferably, the liner has a comparatively-rigid base and is capable of standing, unsupported, outside the reservoir. The side walls of the liner are preferably thin in comparison to the base and can be collapsed for disposal of the liner. The reservoir has a removable lid and is capable of standing, inverted, on its own so that it can be filled with fluid. The lid also functions to secure the liner in the reservoir and, at the end of a spraying operation, the lid and the liner are removed together from the reservoir and discarded, thereby simplifying the cleaning of the spray gun.
These containers typically have a frustum configuration matching the shape of the thin, smooth-walled liner. The frustum shape results from the nature of the manufacturing process which requires a draft angle. However, the fact that the container and liner have a corresponding shape can cause excessive friction between the liner and the container wall during collapse. Furthermore, the smooth walled liner does not provide assistance in the collapsing of the liner, which can cause difficulties, particularly at the beginning of the application process. These problems can lead to diminished surface quality on the painted object.
In addition, the fluid supply assembly must have a fluid tight seal. There are several known sealing methods used in the paint industry. The most common is internal sizing. In this arrangement, there is a circular rib on the bottom of the lid that fits inside the liner. The seal relies on the uniform compression of the rib against the sidewall of the liner. While this method is adequate in many cases, even minor deviations from a perfectly cylindrical shape on either part can cause seal failure. Another method relies on additional facial sealing using the liner lip as a gasket. The liner lip can be compressed directly (matching surfaces), or through a circular protrusion, which localizes the sealing. This method is an improvement over cylindrical compression alone. However, under certain conditions, it may still allow seepage, particularly with low viscosity fluids.
The various paint components must be provided in the appropriate amounts. One method of ensuring the proper mixture is to use a measuring guide. The measuring guide can be located on the inside or on the outside of the container. When the measuring guide is inside the container, there is direct contact between the liner as it collapses and the measuring guide. This contact can cause unintended movement of the measuring guide during use. Movement can also occur when the liner is replaced. Improper location of the measuring guide can lead to improper paint mixtures. External measuring guides have wide longitudinal protrusions which are positioned beyond the natural perimeter of the container. The protrusions can create an awkward grip on the container during use.
Therefore, there remains a need for an improved fluid supply assembly.